This invention relates to electric heaters, and more particularly, it relates to electric heaters suitable for use in molten metals such as molten aluminum.
In the prior art, electric heaters used for molten aluminum are usually enclosed in ceramic tubes. Such electric heaters are very expensive and are very inefficient in transferring heat to the melt because of the air gap between the heater and the tube. Also, such electric heaters have very low thermal conductivity values that are characteristic of ceramic materials. In addition, the ceramic tube is fragile and subject to cracking. Thus, there is a great need for an improved electric heater suitable for use with molten metal, e.g., molten aluminum, which is efficient in transferring heat to the melt. The present invention provides such an electric heater and provides a refractory coating resistant to attack by the molten aluminum.